The present invention relates to a method of workpiece handling in a grinding apparatus of the type which is commonly referred to as a disc grinder, in which a workpiece is moved by a workpiece carrier into a grinding area where one or two parallel surfaces of the workpiece are ground by a surface of a disc which is fed along an axis of the disc into the workpiece.
Such a grinding apparatus is well known in the art. Bendix offers several models of horizontal single and double disc grinders in various sizes under its Bendix Besly trademark. Bendix also offers several vertical single and double disc grinders in various sizes. These disc grinders are especially suited for grinding a precisely located, smooth finish on a part, with a substantial parallelism between ground surfaces ground or finished by a double disc grinder. The horizontal and vertical appellations refer to the axis or direction in which the grinding disc is advanced and not the orientation of the grinding surface, which grinding surface is perpendicular to axis of disc advance. One such grinding apparatus is described in U.S. Pat. No. 3,800,476 of H. J. Fallon entitled "Rotary Work Carrier for a Double Disc Grinder," a patent which is hereby incorporated herein by reference, particularly for its disclosure of disc grinder structure and operation.
In the grinding of some workpieces, such as universal joint crosses, it is desirable to provide a finished or ground surface on four legs, i.e., two parallel surfaces at the ends of each of two intersecting or transverse legs (or arms) of the cross. Such workpieces are advantageously finished by grinding two parallel surfaces on alternate legs, then by rotating or indexing the workpiece by 90 degrees to present the other two unground surfaces on the intermediate legs in an orientation for grinding. After those other two surfaces are ground, the finished workpiece is removed from the grinding apparatus.
One apparatus for grinding such workpieces is disclosed in U.S. Pat. No. 2,990,659 entitled "Work Indexing Means for Disc Grinders." Such an apparatus discloses a rather complicated workpiece handling apparatus for indexing (or rotating by 90.degree.) the workpiece after machining a first set of parallel surfaces. However, such apparatus uses a manual (operator) loading and unloading of the workpiece carrier and does not teach or suggest an automatic loading or unloading of the workpiece carrier. The described apparatus does eliminate the need for the operator to select and manually remove a workpiece and rotate it by hand and replace it. But such workpiece indexing is only one part of the manual labor involved in grinding such crosses.
Previous to the grinding apparatus described in the above patent, cross grinding relied upon an operator's selecting or sorting of partially ground workpieces which the operator then manually indexed and replaced in the carrier. The operator also loaded manually the unground workpieces as well as unloaded the completely ground parts. Such a system is slow, labor intensive, costly and subject to operator error.
Of course, in a rather conventional grinding apparatus the operator could manually load and unload the workpiece carrier and also index the parts manually. Such an apparatus would be very expensive in labor and subject to operator error as well as being limited in the speed of operation.
Accordingly, the prior art grinding apparatus for such workpieces on two sets of transverse sides have disadvantages and limitations, in terms of cost and labor requirements.